The utility that operates Japan’s crippled atomic plant said Friday that it deserves most of the blame for the country’s nuclear crisis, in its strongest remarks about its own shortcomings.

Tokyo Electric Power Co. acknowledged in a report that it was not adequately prepared to deal with the massive earthquake and tsunami that ravaged northeastern Japan in March 2011. The twin disasters cut power at TEPCO’s Fukushima Dai-ichi nuclear plant, causing meltdowns at three reactors. Massive radiation leaks contaminated air, water and soil around the plant, forcing about 160,000 residents to evacuate.

“Our safety culture, skills and ability were all insufficient,” TEPCO President Naomi Hirose told a news conference. “We must humbly accept our failure to prevent the accident, which we should have avoided by using our wisdom and human resources to be better prepared.”

The report said TEPCO’s equipment and safety provisions were inadequate and that the meltdowns should have been avoided. TEPCO said it was complacent about safety measures and delayed upgrading them until after the accident. It also said TEPCO didn’t adequately inform the public of risks and troubles at the plant.

The acknowledgement is a major reversal from TEPCO’s initial investigation report.

In the June 2012 report, TEPCO maintained that the tsunami was mostly to blame for the world’s worst nuclear disaster since Chernobyl in 1986. It defended its crisis management and criticized excessive interference from the Prime Minister’s Office.

After the company’s reluctance to come to terms with its responsibility triggered public outcry, it launched an internal reform task force, led by Hirose, to reinvestigate the crisis. The task force was overseen by a five-member committee of outside experts, including former U.S. Nuclear Regulatory Commission chief Dale Klein.

In October, TEPCO acknowledged that it underestimated the tsunami risk and could have mitigated the impact of the accident if it had backup power and cooling systems and trained employees with practical crisis management skills. Friday’s report urged TEPCO to introduce effective training programs and oversight by outside experts.

Klein said the nuclear industry has to “expect the unexpected and have margins of safety.”

“I do think it would have been appropriate for TEPCO have thought about what they would have done if there would have been a large tsunami and that would have mitigated a lot of actions,” he said. “We are unable to turn the clock back in time and stop the accident. What is important for the reform committee and TEPCO is to move forward, learn from mistakes and make sure that never happens again.”

Critics have raised doubts as to whether TEPCO is seriously trying to change, and an extended blackout at the plant last week was a reminder that the crisis is not over.

The blackout occurred after a rat short-circuited an outdoor switchboard, but TEPCO waited three hours to make an announcement. The outage left four fuel pools without cooling functions for up to 30 hours.

TEPCO officials denied Friday that the incident posed safety threats outside of the plant, but acknowledged they lacked sensitivity about how Fukushima residents felt about the loss of power and cooling.

“We learned that it only takes one rat, not even an earthquake or tsunami, to paralyze the plant,” said Yukihiro Higashi, an Iwaki Meisei University engineering professor who is on a government nuclear regulatory panel overseeing Fukushima Dai-ichi safety.

“People in Fukushima are under constant fear of another serious incident that requires evacuation,” Higashi said.

The full cleanup of the plant, which is still running on makeshift equipment, is expected to take decades.

Officials said Friday that rats and snakes are frequently spotted at the plant, even inside its emergency command center. Rats are particularly a concern because they can chew on power cables and water hoses, said TEPCO official Kazuhiko Yamashita, adding that officials are considering further anti-rodent measures.

The reform plans aim to use the lessons learned at TEPCO’s Kashiwazaki-Kariwa plant in northern Japan. The cash-strapped utility wants to restart the plant, and officials say they have upgraded safety measures, although they have not specified any timeline.

Government, parliamentary and private groups have separately published the results of their investigations into the crisis, largely blaming the disaster on botched crisis management, government-industry collusion and the tsunami.